PURPOSE: During binocular rivalry, transitions in perceptual state can be triggered by abrupt contrast increments within a small region of the currently suppressed pattern. Transitions occur locally and spread throughout the pattern, creating a perceptual wave of dominance1. We developed a novel version of this procedure whereby opposing traveling waves are periodically created, producing time-locked changes in dominance.

METHOD: Observers dichoptically view two vertically elongated rival stimuli and track perceptual fluctuations within a small region of this configuration (monitoring area). During the viewing period, contrast increments (triggers) are alternately, repetitively presented within the upper and lower region of the two rival stimuli, respectively. Ideally, triggers presented to the upper (lower) region of a suppressed pattern should induce a downward (upward) perceptual wave that is evidenced by a delayed perceptual switch at the monitoring area.

RESULTS: We derived probability switch functions for the monitored area to infer the existence of traveling waves. Experiment 1 confirmed that switches in dominance were systematically modulated by the trigger period. Experiment 2 demonstrated that the delay between trigger presentation and perceptual switches was systematically related to the trigger's distance from the monitoring area. In Experiment 3, we presented vertically elongated figures to the two eyes where only the middle portion induced rivalry; monocular triggers were presented within regions of concordant binocular stimulation. Triggers within non-rivaling regions still modulated periodicity of perceptual switches within the region of rivalry, particularly when the trigger was close to the rival area.

CONCLUSION: This novel technique produces reliable perceptual waves whose properties can be inferred from data produced simply by tracking rivalry. This technique reveals that mechanisms underlying perceptual waves during rivalry also operate within regions of binocular fusion.